Differential detection in quadrature-quadrature phase shift keying (Q2PSK) systems
Abstract
A generalized quadrature-quadrature phase shift keying (Q2PSK) signaling format is considered for differential encoding and differential detection. Performance in the presence of additive white Gaussian noise (AWGN) is analyzed. Symbol error rate is found to be approximately twice the symbol error rate in a quaternary DPSK system operating at the same Eb/N0. However, the bandwidth efficiency of differential Q2PSK is substantially higher than that of quaternary DPSK. When the error is due to AWGN, the ratio of double error rate to single error rate can be very high, and the ratio may approach zero at high SNR. To improve error rate, differential detection through maximum-likelihood decoding based on multiple or N symbol observations is considered. If N and SNR are large this decoding gives a 3-dB advantage in error rate over conventional N = 2 differential detection, fully recovering the energy loss (as compared to coherent detection) if the observation is extended to a large number of symbol durations.
- Publication:
-
IEEE Transactions on Communications
- Pub Date:
- May 1991
- Bibcode:
- 1991ITCom..39..703E
- Keywords:
-
- Quadrature Phase Shift Keying;
- Signal Detection;
- Signal To Noise Ratios;
- Bit Error Rate;
- Decoding;
- Maximum Likelihood Estimates;
- Random Noise;
- White Noise;
- Communications and Radar